1. Field of the Invention
The present invention relates to the preparation of N-benzylimides, and, more especially, to the preparation of those substituted or unsubstituted N-benzylimides having the structural formula: ##STR3## wherein Ar is a benzene radical and R.sub.1 is an aliphatic or aromatic hydrocarbon.
By "benzene" radical as utilized herein, there is intended a substituted or unsubstituted phenyl moiety, as hereinafter more fully set forth.
2. Description of the Prior Art
It is known to this art, from West German Pat. No. 2,526,652, to react an optionally substituted trifluoromethylbenzene with N-hydroxymethylphthalimide to yield N--trifluoromethylbenzyl)phthalimides. This reaction is carried out by heating the two reactants to a temperature of about 50.degree. C. for several hours, in sulfuric acid.
Nonetheless, the use of sulfuric acid on an industrial scale is fraught with certain disadvantages. In effect, the product of the reaction is dissolved in the sulfuric acid; furthermore, the water formed during the reaction remains present; and the distillation of the water and H.sub.2 SO.sub.4 is virtually impossible because it requires levels of temperature which are incompatible with the stability of the desired products. It is thus necessary either to dilute the reaction mixture with water to enable extraction with an organic solvent, or to conduct such extraction in a concentrated sulfuric acid medium, which latter is quite difficult and complicated. Furthermore, in the case of fluorine compounds (as is the aforenoted West German patent), the presence of the H.sub.2 SO.sub.4 gives rise to certain objectionable defluoration reactions which are detrimental both economically and technically.
Finally, the oxidizing and sulfonating properties of sulfuric acid give rise to the formation of numerous by-products.